Final answer:
An air gap device prevents the backflow of pesticide liquids into the water source, which prevents contamination and protects human health and the environment.
Step-by-step explanation:
An air gap device creates a physical separation that prevents backflow of pesticide liquids or other contaminants into the water source. This is important because it ensures that the source water remains uncontaminated by any substances that could be potentially hazardous to both human health and the environment.
The correct answer to the question is A. An air gap device creates: A gap between the filling hose and the liquid in the spray tank that prevents backflow of pesticide liquids into the water source.
This strategy helps to mitigate the risk of the liquid in the spray tank being drawn back into the public water system in the event of a decrease in water pressure, thereby contaminating it and potentially creating a health hazard.